Abstract
This paper is focused on the experimental study and numerical simulation of isolated spread concrete foundation slab with a large width-to-height ratio (in short ISCFS-LWR) to investigate the failure modes and uplift bearing capacity, as well as the design method of uplift capacity. First, a total of 16 isolated spread concrete foundation slabs with the width-to-height ratio varied from 1.5 to 4 and the hypotenuse slope varied from 10° to 30° were tested under uplift load. Based on the test results, effects of the width-to-height ratio and the hypotenuse slope on uplift bearing capacity of ISCFS-LWR were analyzed and discussed. Then, several numerical models were built using the finite element software ABAQUS and the results of numerical analysis agreed well with the test results. Furthermore, the cross-sectional performance of ISCFS-LWR was studied, and the coefficients of internal force arm were also evaluated further using previous validated numerical models. To obtain the suggested design method of uplift capacity for the foundation slab, effective width correction coefficientkand slope correction coefficientjwere introduced to propose a design formula. Finally, the proposed design method was applied to a practical engineering, and the economic indicators obtained from the suggested design method were compared with that from the original design method. The results of this paper showed that the correction coefficientjsksbased on numerical analysis agreed well with the recommended correction coefficientjk, and the error was between 1% and 3.4%, by which the reasonability of the proposed design method of uplift capacity for ISCFS-LWR has been proved. It can also be found that the economic benefits of the practical engineering in this paper were obvious due to the suggested design method, and this paper can provide a reference for other engineering practices and the further research work on ISCFS-LWR.
Highlights
As one of the main forms of transmission tower foundations, isolated spread concrete foundation has been widely used in transmission lines recently because of its efficiency and economy. e foundation in transmission lines can be subjected to the downward load and can be affected by the uplift load, so it is necessary to consider double-layer reinforcement for the foundation slab
From the comparison of the average value Fave between the specimens NJ1(NJ9), NJ2(NJ10), NJ3(NJ11) and the specimens NJ4(NJ12), NJ5(NJ13), it showed that the uplift bearing capacity reduced gradually with the increase of the hypotenuse slope when the width-to-height ratio, the size of the foundation slab, and the steel reinforcement were the same
Based on the above numerical model and the reasonable finite element analysis method, the further analysis was conducted to study the effect of the width-to-height ratio and the hypotenuse slope on the cross-sectional performance of the ISCFS-LWR under the uplift load
Summary
As one of the main forms of transmission tower foundations, isolated spread concrete foundation has been widely used in transmission lines recently because of its efficiency and economy. e foundation in transmission lines can be subjected to the downward load and can be affected by the uplift load, so it is necessary to consider double-layer reinforcement for the foundation slab.Many successful researches on foundations, which subjected to the uplift load, have been reported. Uplift tests were conducted to study the law of crack expansion and deformation characteristics of spread foundations under a combination action of uplift and horizontal loads [12]. Failure modes and bearing capacity of the concrete foundation slab itself under the uplift load have rarely been developed, especially the research on the design method of uplift capacity for the isolated spread. Ere are three types of towers in this project, and the acting forces of the foundations are shown, where Tmax is the maximum uplift load of the foundation, Tx is the horizontal force along the direction X when subjected to the uplift load, Ty is the horizontal force along the direction Y when subjected to the uplift load, Nmax is the maximum downward pressure of the foundation, Nx is the horizontal. Project. e name of this engineering is 500 kV wild peach line relocation project, which is located in the southeast edge of Chengdu Plain in China. e landform and geomorphological features mainly include the accumulation ridge platform, strip-shaped denudation shallow hill, low mountain, gentle slope platform, and other landforms, as shown in Figure 16. e form of the foundation adopts the universal design module of the State Grid.
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